A semiconductor manufacturing process includes steps of coating the surface of a semiconductor wafer with a resist, then exposing and developing the wafer, thereby forming a mask corresponding to a predetermined pattern. These steps require connection of a coating/developing unit and an exposure unit in accordance with development of FA and enlargement of the diameter of wafers. The reason why the coating/developing unit is separated from the exposure unit will be explained below.
Light, X-rays, electron beams, ion beams, etc. are considered pattern information transmission mediums used in an exposure step. Different types of exposure units must be used depending upon the types of mediums or patterns. On the other hand, in the coating/developing process, different steps can be dealt with by changing the types of resists or developers or changing the treatment period of, for example, baking. Concerning the hardware structure, there are lots of sections which can be commonly used, and hence a single apparatus can be commonly used for the different steps. This being so, the coating/developing unit is not formed integral with the exposure unit and has a separate structure from it.
Each of the coating/developing unit and the exposure unit includes a control unit such as a personal computer, through which start of the units, start of the input of a lot, or input of a recipe can be instructed manually. In a semiconductor manufacturing factory, multiple pairs of coating/developing units and exposure units are installed on a single floor, and controlled by a host controller.
In the conventional structure for performing such control, plural pairs, e.g. six pairs, of coating/developing units and exposure units are connected to plural remote controllers, which are connected to a host computer for controlling the entire floor. Each unit of each pair is connected to a corresponding remote controller by connecting the interface of a control unit (personal computer) incorporated in the unit, to a corresponding remote-controller-side interface using a cable.
Each remote controller stores, in relation to respective identification codes, pairs of recipes which are combinations of recipes (process recipes) for coating/developing treatments and those for exposure treatments. When the remote controller has received identification codes from the host computer, or when identification codes have been manually input through the operation panel, the remote controller selects the pair of a coating/developing recipe and an exposure recipe which corresponds to the identification codes, thereby downloading the recipes to the coating/developing unit and the exposure unit, respectively.
Each unit of each pair can be controlled by manually operating a corresponding operation panel to set or instruct a process step. In the case of using a remote controller, it supplies corresponding units with a start instruction, an instruction to switch lots or to exchange reticles, and selected coating/developing and exposure recipes. These units, in turn, supply the remote controller with information concerning the degree of advancement of process, process results, alarm output, etc. Moreover, the control unit of the coating/developing unit is connected to that of the exposure unit by a cable for transmitting a timing signal for wafer transfer. In other words, when a wafer is transferred by transfer means between each pair of units, a timing signal is supplied from one of the units to the other, so that a transfer unit on the coating/developing unit side, a transfer robot on the exposure unit side and a transfer robot located therebetween can operate in a predetermined sequence, thereby enabling automatic transfer of a wafer between the units. The timing signal is supplied when each robot operates.
The conventional central control apparatus, however has the following problems:
(1) It is difficult to perform fine control since the amount of processing load on the remote controller is great because of a great amount of communication. More specifically, since the remote controller centrally controls multiple coating/developing units and exposure units, the amount of communication and the load of processing will become great if the remote controller fetches detailed information on, for example, the position of each wafer and outputs a control command to each unit. On the other hand, in the coating, exposing and developing steps, a time (a tact time) required from the end of a step to the start of the next step must be entirely strictly controlled. Where a fine treatment of an order of, for example, 0.25 .mu.m is performed using a chemical amplification resist and i-ray exposure, it is necessary to strictly control the treatment time from the end of exposure to pre-baking. In this case, the remote controller must periodically fetch information on the position of each wafer, by communication, from the coating/developing unit and exposure unit, and output appropriate control instructions. This is a great load on the remote controller.
Further, the coating/developing treatments and exposure treatment are carried out on the basis of coating/developing and exposure recipes which correspond to the type of each wafer. A recipe used in each unit is changed by downloading a new one from the remote controller to the unit. Since one recipe, particularly an exposure recipe, contains lots of information such as exposure amount, wavelength, exposure period of time, etc., downloading of the recipe from the remote controller side to each exposure unit requires execution of a great amount of communication, which means extreme inefficiency.
In addition, lots of connection cables are provided between the remote controller and each unit. Including cables between the remote controller and the host computer, a great number of cables are arranged on the entire floor, which may interrupt the work on the floor and degrade the reliability of the system. Furthermore, if the remote controller breaks down, the coating/developing units and the exposure units under its control will inevitably break down.
This invention is aimed at providing a control apparatus for a processing system, which can enhance the efficiency of the entire system and easily perform fine control of components in each processing station.